Exhaust gas recirculation (EGR) may be used in internal combustion engines to decrease emissions, as well as improve combustion efficiency and fuel economy. Some EGR systems may draw exhaust gas from a location downstream of a turbine and flow the exhaust gas to the intake system. These types of EGR systems may be referred to as low pressure EGR systems.
U.S. Pat. No. 7,801,669 discloses an engine with a low pressure ERG loop. Specifically the EGR conduit is fluidly coupled to an exhaust conduit downstream of a turbine and a particulate filter. During selected operating conditions, exhaust gas may be directed through the EGR loop. By positioning the junction of the EGR conduit and the exhaust system downstream of the particulate filter, fouling of the EGR conduit may be reduced.
However, the Inventors have recognized several drawbacks with the EGR system disclosed in U.S. Pat. No. 7,801,669. The turbine and particulate filter may increase losses within the exhaust gas flowing through the exhaust system thereby decreasing the flowrate of exhaust gas traveling through the EGR conduit. Furthermore, losses within the EGR conduit may be large due the geometric configuration (e.g., T-Junction) of the confluence between the EGR conduit and the turbine outlet exhaust passage. Specifically, the tangential component of the gas flow may cause a large amount of flow separation and turbulence in the inlet to the EGR conduit. As a result the EGR system's efficiency may be decreased.
As such in one approach, an exhaust gas recirculation (EGR) system in a vehicle is provided. The EGR system includes a turbine fluidly coupled downstream of an exhaust manifold and an EGR conduit including a first port coupled to an exhaust passage directly downstream of the turbine, an axis of the first port arranged at a non-perpendicular angle with respect to the rotation axis of the turbine and a second port coupled to an intake system. In this way, the EGR conduit inlet may be integrated into the turbine housing, thereby decreasing losses and increasing EGR efficiency and therefore engine efficiency during selected operating conditions.
It has been discovered that when the EGR port is positioned in this way, the losses within the EGR system may be decreased. Specifically, the structural design (e.g., orientation of the EGR conduit) enables the tangential component of the exhaust flow exiting the turbine to drive flow through the EGR system to increase the volumetric flow of the exhaust gas through the EGR conduit.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.